Few empirical investigations have been conducted examining sibling relationships among youth in foster care, and even fewer have explored relationship warmth as a protective factor. With a sample of 246 youth from a non-profit organization's summer camp program, Camp To Belong, this study examined the association between a warm sibling relationship and resilience for youth in foster care. A warm sibling relationship significantly predicted individual resilience for both middle childhood and adolescence developmental periods. Younger youth with poorer sibling relationship warmth had lower resilience. The implications of these findings are important given that resilience is a factor associated with improved outcomes in the face of adversity. The promotion of sibling relationships, a readily available resource, can be drawn upon by those in clinical practice to improve outcomes for youth in foster care.